This invention relates generally to the art which is concerned with producing fuel gas from organic material, and more particularly concerns an apparatus and method in such art which is self-sustaining in operation.
The use, per se, of a pyrolysis process to convert organic material, such as wood chips, to fuel gas and charcoal is well known, and a wide variety of devices have been designed to accomplish such a result. A primary disadvantage of such devices, which are generally referred to as gasifiers, is that a typical by-product of the pyrolysis process is a large quantity of tars, which affect both the operation of the gasifier, eventually clogging it, and the end use apparatus of the gas, such as an internal combustion engine or other burner of some kind. This problem is particularly prevalent in portable gasifiers, which are generally known as gasogens. The problem is discussed in detail in application Ser. No. 018,118, filed Mar. 7, 1979, now U.S. Pat. No. 4,268,275, titled: Apparatus and Method for Converting Organic Material Into Fuel, by the same inventor named on this application. The solution disclosed in that application included a reaction chamber having a pyrolysis zone followed by a reaction zone comprising a bed of charcoal heated to a high temperature. The high temperature of the charcoal and the catalytic effect of the ash residue on the surface of the hot charcoal break down the tars from the pyrolysis zone into carbon monoxide and hydrogen. The heat for the pyrolysis zone and the reaction zone was provided externally.
Such a unit, which is effective and useful in many applications, is not particularly useful in a portable mode, i.e. such as on a vehicle. Also, the start-up time and response to demand of such units are typically very slow, significant disadvantages in a portable unit. Also, the proper operation of most gasifiers is confined to rather narrow parameters, and even then is somewhat unpredictable, as such units are still prone to produce tar, and are subject to additional problems such as channeling and clinkering. Such units typically operate best at a steady state, rather than with a variable demand. Further, such units typically produce an excess of charcoal, which requires monitoring and removal systems, and which can lead to more serious operational problems. Hence, for many applications, particularly those requiring a portable unit, conventional gasifiers are impractical economically and therefore at the present time have a rather low market significance.
Accordingly, it is a general object of the present invention to provide a method and apparatus for producing fuel gas from organic material which overcomes one or more of the disadvantages of the prior art noted above.
It is another object of the present invention to provide such a method and apparatus which is specifically adapted to be portable, and hence may be conveniently used on a vehicle.
It is an additional object of the present invention to provide such a method and apparatus which is characterized by a relatively rapid start-up time.
It is yet another object of the present invention to provide such a method and apparatus which is characterized by a relatively rapid response to changes in demand.
It is a still further object of the present invention to provide such a method and apparatus which is capable of operating satisfactorily over a relatively wide range of demand.
It is an additional object of the present invention to provide such a method and apparatus which produces tar-free fuel gas, and which is not prone to clinkering or channeling.